US 2324236 A
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July 13, 1943. N. c. PRICE BLOWER AUTOMATIC THROTTLE Filed June 10, 1939 Snvcntor Nathan C-Price Gttorneu Patented July 13, 1943 BLOWER AUTOMATIC THROTTLE Nathan C. Price, Seattle, Wash., assignor, by
mesne assignments, to Boeing Aircraft Oomiplimy, Seattle, Wash, a corporation of Wash- Application June 10, 1939, Serial No. 278,523
A blower is employed in maintaining the pressure within an aircraft cabin at a desirable pressure density, above atmospheric, at high altitudes.
Such a blower, or the air discharged therefrom, is regulated by a more or less complicated automatic or semi-automatic device controlling the amount of air admitted to the cabin and the amount discharged therefrom to maintain the proper pressure level, in accordance with atmospheric conditions and altitude. Arrangements to this end are disclosed in detail in my Patent No. 2,208,554 issued July 16, 1940, and in my copending application, Serial No. 216,028, filed June 27, 1938, respectively.
It is undesirable to permit too great or too rapid development of differences of pressure between the intake to and the discharge from the blower. For instance, it is intended in such cabin supercharging systems as are disclosed in my patent and copending application referred to above, to have the blower directly connected to a propelling engine of the airplane, and to have its discharge duct into the cabin throttled to produce a constant flow at altitudes below, say 8000 feet. Below this altitude such air delivered will merely be replacement air, for the cabin air pressure is equal to atmospheric, not being supercharged until a higher altitude is reached. Unless the flow is held constant by throttling, the blower will tend to pass great quantities of air, absorbing far greater power than if it were not throttled. Upon take-off at sea level, where the atmosphere has maximum density, and with the engine developing power approaching its maximum, that is to say, developing considerably more power and operating at higher speed than during cruising, it will be understood that such a blower throttled only at its discharge may well develop a very considerable difference of pressure (perhaps as much as 30 inches of mercury) as between its intake, which may or may not be under minus pressure, and its discharge duct, which is at appreciable plus pressure. This situation exists because the blower has been designed to produce a given pressuren'ise, inches of mercury for example, at an altitude of 20,000 feet (where, because of the airs slight density, the blower must handle large quantities) and during cruising engine speed, which requires materially less power than is used at take-off. Because, then, the system must be designed to operate under high altitude conditions, it produces magnified and undesirable effects under take-oil conditions, and particularly at sea level. Then, also,
' such pressure differences are accompanied by undesired and disadvantageous temperature effects, particularly abnormal rise of temperature in the discharge duct, which is supplying air to the cabin, caused by high compression of air in it when nearly closed off. These conditions result in excessive power consumption by the blower, and adversely affect the control mechanism which must be prepared to hold down the excessive flow tendencies by throttling the discharge, and then to resist the extreme pressure rise resulting from the throttled discharge. Sensitive controls are generally not intended to operate at such pressures. Furthermore, appreciable noise is produced in the blower discharge duct and through the control mechanism. It is the object of the present invention, then, to provide means to throttle the blower, normally the intake thereto, to limit the pressure differential as between the blower intake and the blower discharge to a selected maximum, perhaps to sixteen inches of mercury under the most extreme conditions, to the end that the diil'erential between the blower intake and the blower discharge duct is automatically limited, that there is a lower temperature rise in the blower discharge duct, that there is less power consumption by the blower, that the automatic controls may have greater sensitivity since they are not subjected to such excessive pressure difierences, and that there is less noise developed by the supercharging equipment.
It is also an object to provide mechanism of the character indicated, which shall be simple yet effective, rugged and requiring little or no attention, and which is light in weight.
With these and other objects in mind, as will appear hereafter, my invention comprises the novel parts, and the novel arrangement thereof relative to the blower intake and discharge ducts, and relative to the cabin supercharging and pressure controlling equipment.
In the accompanying drawing I have shown myinvention embodied in a typical form and in a representative installation, it being understood that various changes may be made in the form, arrangement, and character of the parts, as will appear more fully hereinafter.
Figure 1 is an elevation largely diagrammatic in character, and with parts broken away, illustrating the arrangement of the throttle relative to the blower and relative to the cabin pressure automatic control mechanism.
Figure 2 is an enlarged section through the damper and its operating mechanism, which comprise the automatic throttle, shown in relation to the blower intake duct, and Figure 8 is a further enlarged axial section through the pressure cylinder, illustrating the piston which v is reciprocable therein.
The cabin structure of the aircraft is indicated at I. .This structure is made air-tight, at least sufiiciently so that there will be no undue leakage of air from within, though the cabin pressure may exceed the external atmospheric pressure by an appreciable amount, such as inches of mercury for example. At high altitudes, air is supplied to the cabin from the external atmosphere by a blower I which is normally directly connected tonne of the propulsive engines (not shown), whereby the blower rotor is driven at.a
speed corresponding to the speed of the engine.
the leading edge of the wing. Thisair at high altitudes is considerably more rarefied than at sea level, and, for any given speed of the engine and blower I, the air is less dense when delivered through the blower discharge duct 82 and into the cabin, the higher the altitude. To put it diflerently, at sea level, where the atmosphere is at maximum density, at a given blower speed,
which is dependent upon engine speed, the air will be discharged through the duct 02 and into the cabin I at rather high pressure as compared to the discharge pressure with the same engine speed at 8 1 fltitudes, say at 20,000 feet, for at thehighaltitudesthemtaken airis somuch less dense at sea levehand consequently at a given blowerspeedcan only be compressed to'apressure density which is considerably lower than the pressure density to which air at sea level pressure may be condensed at the same blower speed. If, then, the blower speed is higher at sea level, for instance at take-oil, then the pressure in the discharge duct 02 is even greater.
Thedischargeduct l2 delivers airpast acabin pressurecontrol unit I, having an inlet valve II, the intermittent opening and clodng action of which is controlled by rather complicated and sensitive mechanism fully described in my aforementioned Patent No. 2,208,554, and into the cabinattheexitfl. Airisdischargedfrom the cabinpastanoutletvalve'lltoacabinoutlet duct l2,andtheoutletvalve1l is likewise controlled by rather complicated and sensitive mechanism. This pressure control device I operates automatically, and being sensitive, it must be protected insofar aspossible from extremes of blower discharge pressure or temperature. Likewise, at such extreme blower discharge static pressures, which are inversely variable with the velocity of flow throttled by closing movement of inlet valve II, it islikely to become noisy and to operate unsatisfactorily, and'in any event excessive temperature effects are produced, and the blower consuma an unduly large proportion of the power of the engine, whereas the engine parflcularly requires all available power at takeoil'. It is for such reasons that the automatic blower intake throttle is emp oyed.
This throttle consists of a damper I, pivotally mounted upon a transverse axis at It, within the blower intake duct ll. Preferably the damper includes two portions disposed at an obtuse angle, that is, greater than a right angle and slightly less than a straight angle, so that one arm may lie parallel to .theair flow, with the other am inclined somewhat in such a way that the action of the pressure diflference upon opposite sides of the damper normally tends to keep the damper open, the force thus acting being variable with the degree oi pressure diiierence. It is also held open by yieldable means consisting of a spring I acting upon an element 3 in the form of a piston reciprocable within a casing or cylinder 30, and connected by a stem ll, adjustable in length, to the damper I. The connection may be by means of an antifriction bearing at Ii, offset from the pivotal mounting IO oi the damper. The action of the spring 2 urges the piston 3 and its stem 3| upwardly, thereby tending to hold the damper open.
The cylinder 30, at its lower end, is vented, as indicated at 32, to avoid entrapment of air as the piston tends to move downwardly in a direction to close the damper, yet the vents are sufficiently small so that a dash pot action results if the pressure builds up too rapidly. Provisions are also made in the arrangement of the piston and its connection to the damper to accommodate and permit oscillating movement of the piston, which need only be slight. Thus as seen in Figure 3 the skirt of the piston is rather short axially, and is rounded so that the piston may oscillate. It need hold only slight pressure, hence a, reasonably close fit over a short distance will suifice. Also, as is seen in Figure 2, the cylinder "is mounted directly upon the blower intake duct II, and a hole is formed for the accommodation of the stern II, which hole is larger than the stem, but which is closed by a washer 33 which is slidably held in a cage 34. In this manner the piston I and its stem 3! may oscillate, as required by its direct connection to the pivoted damper, yet no undue leakage, either into the duct II or past the piston 3, will result.
. The cylinder 30 is connected by a short length of tubing 4, fitted to the cylinder at 35, to the blower discharge duct .2, leading to the cabin and to the pressure control apparatus 1. The
ducts II and 82 may in this portion parallel each other, though that, of course, is not an essential, since the connecting tube 4 may take any form desired.
Pressure in the blower discharge duct-l2, which builds up as valve 10 moves toward closed position to restrict the duct and throttle the blower's output, is, by the connection 4, communicated to the cylinder 30 and to the upper face of the piston 3. The force resisting the tendency of such pressure to close the damper is the spring 2, which may be adjusted, by the use of shims or in any suitable way, to supply the desired amount of resistance. Once this limit of resistance is overcome by the pressure acting upon the upper and the blower discharge pressure acting upon the upper side of the piston through the duct '2 and the connection 4. Thus the damper may 'be set to close substantially wholly at some such selected difference of pressure, though preferably it does not close altogether as is shown by the dotted line showing in Figure 2, and in this manner an excessive difference in pressure in the duct 82 over the atmospheric pressure and'over the suction in the blower intake duct BI is prevented. The stop flange l2, in position to engage the damper l in the closed limit of its movement, prevents the damper going beyond the dotted line or fully closed position.
During closure or partial closure of the damper I the supercharger operates in a partial vacuum. relative to atmospheric pressure, and under such condition of operation in the less dense medium is caused to do less work upon the air passing through it.
It has been found during test of one'pressure cabin aircraft under take-off conditions that the pressure rise in the blower could be reduced from 30 down to approx mately 16 inches of mercury by installing the apparatus of the invention,
' intake thereto and a discharge duct therefrom,
comprising means to control the amount of air admitted to the blower, means in the discharge duct operable to reduce the velocity of air fiowing out through it and consequently tending to increase the static pressure therein, and means operable automatically under the influence of an increase in pressure in the discharge duct caused bysuch decrease in flow velocity therethrough to operate said control means to lessen the amount of air admitted to the blower, thereby in turn to reduce the degree of static pressure increase in the discharge duct from that which would normally be induced by such decrease in flow velocity.
2. Control mechanism for a blower having an intake thereto and a discharge duct therefrom, comprising means to vary the size of the intake,
means to throttle the blower output, and means operable under the influence of static pressure in the discharge duct, inversely variable with the velocity of flow therethrough, to govern the first means, to decrease the intake automatically in accordance with increase of pressure in the discharge duct induced by the throttling of said second means and the consequent decrease in the velocity of dischargeduct flow, whereby to maintain a. substantially constant differential of blower delivery pressure over blower intake pressure.
'3. Control mechanism for a blower having an intake thereto and a discharge duct therefrom, comprising a damper in the intake movable to control the amount of air admitted to the blower, means operable to restrict the discharge duct and thereby to substantially throttle the blowers output, and correspondingly to increase the pressure in such discharge duct, and means sensitive to suchpressure increases in such discharge duct intermediate the blower and said restrictive means, operable by increase of pressure in such portion of the discharge duct above a selected maximum to move said damper towards closed position.
4. In a system for control of pressure within an the pressure in that portion of said delivery duct intermediate said blower and said control means, for controlling said damper to vary the restriction in said intake duct eflfected thereby.
5. Controlmechanism for a blower having an inlet duct, comprising a delivery duct delivering the entire blower output at all times, means in the delivery duct operable to substantially close such duct, thereby greatly increasing the pres sure therein, a damper in the inlet duct operable to restrict flow therethrough, pressure responsive, damper operating means for controlling said damper to vary the restriction in said intake duct eifected thereby, and a duct connected to that portion of the blower delivery duct intermediate the blower and said first means and communicating with said pressure responsive, damper operating means, for controlling said damper operating means in response to pressure variation in such portion of the blower delivery duct.
6. In a system for control of pressure'within an aircraft cabin, a blower, an intake duct to said blower from atmosphere, a delivery duct to the cabin, means to restrict said delivery duct in governing the cabin pressure, and thereby to substantially throttle the blower output, and means operable under the influence of a pressure diiferential between said intake duct and that portion of said delivery duct intermediate said blower and said restrictive means in excess of a predetermined diflerential, to decrease the intake to the blower, thereby to lessen the aforesaid differential.
7. In a system for control of pressure within an aircraft cabin, a blower, an intake duct to said blower from atmosphere, a delivery duct conducting'the entire blower output at all times to the cabin, means to restrict said delivery duct in governing the cabin pressure, spring-loaded pressure sensitive means operatively connected to be subject to the pressure in that portion of the delivery duct intermediate said blower and said re strictive means, and to be moved in opposition to the spring by an increased delivery duct pressure in excess of a predetermined maximum, and means operated by such movement'of said pressure sensitive means to decrease the intake to the blower, thereby, at the current blower speed, to decrease the pressure in such portion of the delivery duct.
8. Control mechanism for a blower having an intake thereto and a discharge duct therefrom,
comprising a damper in the intake oscillatable' about a transverse axis to control the amount of air admitted to the blower, a cylinder mounted upon the intake, offset from the damper, a piston reciprocable within the cylinder, and operatively connected to swing the damper, means operable to restrict the discharge duct and thereby to substantially throttle the blower's output, and correspondingly to increase the pressure in such discharge duct, a pressure connection from such blower discharge duct, intermediate the blower and said restrictive means, to the cylinder, so arranged that presure in such portion oi the discharge ducttendstomovethepistoninadirectiontoclosethedampenandalprlngopposing such movement at the piston, and aiiording an initial resistance, governing the pressure diii'erential between such portion of the discharge duct and the intake.
9; An aircraft cabin superchars'ing system comprising, in combination. an engine-driven blower, an intake duct thereto from the atmosphere, a discharge duct conducting the entire blower output at all times to the cabin, cabin pressure automatic control mechanism operable to throttle said blower discharge duct to regulate the amount 01'- air supplied to the cabin, thereby increasing the pressure in that portion or said discharge duct between said blower and said control mechanism, a normally open damper in the blower intake, a piston movable within a chamber, and operatively connected to efl'ect movement of the damper, a pressure connection between the chamber and that portion of the blower discharge duct intermediate the blower and the cabin pressure control mechanism, to effect movement of the piston, and yieldable means to govern the pressure at which the piston moves the damper toward closed position, thereby to govern the maximum diilerential of pressure in such portion of the blower discharge duct over the blower intake duct.
10. Control mechanism for a blower havin an inlet duct and a delivery duct, comprising a damper pivot disposed transversely of the inlet duct, a damper plate for restricting now to the V blower through the inlet duct pivoted thereon with one portion or such plate projecting generally radially rrom'such pivot for a greater distancethantheeflectiveextentoftheplatein the precisely opposite generally radial direction, the pressure din'erence in such inlet duct on onposite sides of said damper thereby urging such first damper plate portion toward alignment with the air flow through the duct with a force variable with such pressure dln'erence, and damper operating means operable to move said damper toward closed position in opposition to the cited; of such air flow.
11. Control mechanism tor a blower having an inlet duct and a delivery duct, comprising a damper pivot disposed transversely oi the inlet duct, a damper for restricting flow to the blower through the inlet duct molmted on said pivot and including a vane extending generally radially from one side of said pivot at an obtuse angle to a second vane extending generally radially from the opposite side of said pivot, such relative dispositio of said vanes enabling the pressure din'erence in such inlet duct on opposite sides of said damper to urge said damper toward open position with a force variable with such pressure difierence, b the pressure diflerential acting on said two vanes being unequal. and resilient damper operating means operable to move said damper toward closed position in opposition to the eil'ect of such air flow.
NATHAN C. PRICE.